1. Field of the Invention
The present invention relates to a reader and a recorder in a facsimile machine which is capable of maintaining a picture size compatibility between a facsimile machine whose specifications are set to be expressed in terms of an inch unit system with respect to a picture element density in a main-scanning direction and a scanning line density in a sub-scanning direction perpendicular to the main-scanning direction, which is also capable of maintaining the picture size compatibility between a facsimile machine whose specifications are set to be expressed in terms of a metric unit system with respect to the picture element density in the main scanning direction and the scanning line density in the sub-scanning direction, respectively.
2. Description of the Related Art
The specifications of a facsimile machine are standardized as groups 1, 2, 3 and 4 [G1, G2, G3 and G4) by the Comite Consultatif nternational Telegraphique et Telephonique (nternational Telegraph and Telephone Consultative Committee; which will be referred to merely as the CCTT).
Facsimile machines based on the G3 and G4 specifications handle picture signals in the form of digital data. The picture resolutions of the facsimile picture resolutions in accordance with the G4 specifications are expressed based o the inch unit system. For this reason, when it is desired to transmit a picture signal to a G4 facsimile machine from a G3 facsimile machine which has a G4 facsimile communication procedure and can communicate with the G4 facsimile machine, or when it is desired to transmit it to a G3 facsimile machine from a G4 facsimile machine which has a G3 facsimile communication procedure and can communicate with the G3 facsimile machine; a picture resolution transformation between the metric and inch unit systems is carried out usually at the time of reading an original document.
Take the picture resolution of the G3 facsimile machine for instance. Then the pixel density in the main scanning direction is set at 8 pixels/mm and the scanning-line density in the sub-scanning direction is set at 7.7 lines/mm. In the case of the picture resolution of the G4 facsimile machine, on the other hand, the pixel and scanning-line densities are set at 200 pixels/inch in the main scanning direction and at 200 lines/inch in the sub-scanning direction respectively.
For this reason, when it is desired to transmit a picture signal from a G3 facsimile machine having the G4 facsimile communication procedure to a G4 facsimile machine, the pixel density in the main scanning direction must be transformed from 8 pixels/mm to 200 pixels/inch (200 pixels/25.4 mm). To this end, the picture signal is only required to be subjected at the side of the G3 facsimile machine to a reduction processing having such a reduction factor as shown by the following equation (1), thus providing a picture having the same size as at the G4 machine side with respect to the main scanning direction. EQU (1/8)/(25.4/200)=250/254(=98.43%) (1)
With regard to the sub-scanning direction, the scanning-line density must be transformed from 7.7 lines/mm to 200 lines/inch (200 lines/25.4 mm). This can be attained by performing an enlargement processing having such an enlargement factor as shown by the following equation (2) at the side of the G3 facsimile machine to thereby provide a picture having the same size as at the side of the G4 facsimile machine with respect to the sub-scanning direction. EQU (1/7.7)/(25.4/200)=10000/9779(=102.26%) (2)
Conversely, when it is desired to transmit a picture signal from the G4 facsimile machine having the G3 facsimile communication procedure to the G3 facsimile machine, it is necessary to transform the pixel density of the main scanning direction from 200 pixels/inch (200 pixels/25.4 mm) to 8 pixels/mm, for which purpose the picture signal is only required to be subjected to an enlargement processing having such a factor as shown by the following equation (3) at the side of G4 facsimile machine, thus yielding a picture having the same size as at the side of the G3 facsimile machine with respect to the main scanning direction. EQU (25.4/200)/(1/8)=254/250(=101.60%) (3)
It is also necessary to transform the scanning line density of the sub-scanning direction from 200 lines/inch (200 lines/25.4 mm) to 7.7 lines/mm. This can be attained only by performing a reduction processing having such a reduction factor as shown by the following equation (4) at the side of the G4 facsimile machine to obtain a picture having the same size as at the side of the G3 facsimile machine with respect to the sub-scanning direction.
(25.4/200)/(1/7.7)=9779/10000(=97.79%) (4)
Referring to FIGS. 7(a) to 7(d), there are shown enlargement and reduction factors which are used when a picture signal is transferred between two facsimile machines respectively.
More in detail, FIG. 7(a) shows a processing state when a picture signal is transmitted from a G4 facsimile machine of specifications both based on the inch unit system with respect to the both main-scanning and sub-scanning directions to a G3 facsimile machine of specifications based on the metric unit system with respect to the both main-scanning and sub-scanning directions. The G4 facsimile machine performs a 101.60% enlargement processing with respect to the main scanning direction while performing a 97.79% reduction processing with respect to the sub-scanning direction, and then transmits the picture signal to the G3 facsimile machine.
FIG. 7(b) shows a processing state when a picture signal is transmitted from the G4 facsimile machine of specifications both based on the inch system with respect to the both main-scanning and sub-scanning directions to another G4 facsimile machine of the sam type. The picture signal is not subjected to any enlargement or reduction processing with respect to the both directions at the sender facsimile machine, and then transmitted as it is to the receiver one.
FIG. 7(c) shows a processing state when a picture signal is transmitted from the G3 facsimile machine of specifications both based on the metric system with respect to the both main-scanning and sub-scanning directions to the G4 facsimile machine of specifications based on the inch system with respect to the both main-scanning and sub-scanning directions. The G3 facsimile machine performs a 98.43% reduction processing with respect to the main scanning direction while performing a 102.26% enlargement processing with respect to the sub-scanning direction, and then transmits the picture signal to the G4 facsimile machine.
FIG. 7(d) shows a processing state when a picture signal is transmitted from the G3 facsimile machine of specifications both based on the metric system with respect to the both main-scanning and sub-scanning directions to another G3 facsimile machine of the same type. The picture signal is not subjected to any enlargement or reduction processing with respect to the both directions at the sender facsimile machine, and then transmitted as it is to the receiver one.
Such enlargement and reduction processings have been so far carried out to realize a picture resolution transformation with respect to the main scanning direction by changing the magnifying factor of an optical reading system and also to realize a picture resolution transformation with respect to the sub-scanning direction by changing the ratio of gears sub-scanning a transmission original sheet in the sub-scanning direction. The employment of this method, however, has involved the complicated optical and mechanical arrangement, thus leading to a high manufacturing cost.
Further, there has been known an arrangement for electrically reducing or enlarging a picture with respect to the main-scanning direction in order to relatively reduce the costs required.
An arrangement for electrically reducing or enlarging a picture with respect to the main scanning direction is shown in FIG. 8.
First of all, in the case of reducing a picture, a binary picture signal is inputted to a thin-out sampling circuit 101. The circuit 101, when sequentially receiving the components of the picture signal corresponding to pixels arranged in the main scanning direction, thins out a predetermined number of components from the picture signal at predetermined constant intervals and outputs the picture signal being not thinned-out. When a reduction factor is 98% for example, it is required to reduce every 50 pixels to 49 pixels and thus to remove one component corresponding to one pixel from every 50 components of the picture siqnal corresponding to 50 pixels.
In the case of enlarging a picture, a picture signal is applied to an interpolation processing circuit 102. The circuit 102, when sequentially receiving the components of the picture signal corresponding to pixels arranged in the main scanning direction, interpolates the picture signal at predetermined constant intervals and outputs an interpolated picture signal. When an enlargement factor is 102% for example, it is required to enlarge every 50 pixels to 51 pixels and thus to add one component corresponding to one pixel to every 50 components of the picture signal corresponding to 50 pixels. In this connection, the value of a picture signal component to be interpolated may be a value obtained through linear interpolation based on the value of a picture signal component adjacent to the former picture signal component or may be the same value as the value of a picture signal component previous by one component thereto. In either case, it is necessary to provide a memory 103 for once storing therein the picture signal inputted to the interpolation processing circuit 102.
In the case of electrically reducing a picture with respect to the sub-scanning direction, it is required to thin out a predetermined number of lines from lines of the picture signal arranged in the sub-scanning direction; whereas, in the case of enlarging a picture with respect to the sub scanning direction, it is required to interpolate the picture signal at predetermined line intervals.
Since the reduction processing means to convert a data quantity to a less one, the degree of deterioration in the picture data may be small. However, the enlargement processing means to convert a data quantity to a larger one and this requires the prediction of the value of a data quantity, thus inevitably causing the deterioration of the picture data.
As has been mentioned above, since the prior art facsimile machines have been arranged so that the G3 facsimile machine has specifications of the metric unit system both with respect to the main-scanning and sub-scanning directions while the G4 facsimile machine has specifications of the inch unit system with respect Lo the both directions, which has resulted in that when it is desired to transfer a picture signal between different-group facsimile machines, this requires both the enlargement and reduction processings.
In addition, the necessity of use of the enlargement processing to convert a data quantity to a larger one has disadvantageously involved the inevitable deterioration of the picture data.